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IGMP snooping show commands
Enabling fast leave for IGMP V2
When a device receives an IGMP V2 leave message, it sends out multiple group-specific queries. If
no other client replies within the waiting period, the device stops forwarding traffic. When
fast-leave-v2 is configured, and when the device receives a leave message, it immediately stops
forwarding to that port. The device does not send group specific-queries. When fast-leave-v2 is
configured on a VLAN, you must not have multiple clients on any port that is part of the VLAN. In a
scenario where two devices connect, the querier device should not be configured for fast-leave-v2
because the port might have multiple clients through the non-querier. The number of queries, and
the waiting period (in seconds) can be configured using the ip multicast leave-wait-time command.
The default is 2 seconds.
To configure fast leave for IGMP V2, enter the following commands.
Brocade(config)#vlan 20
Brocade(config-vlan-20)#multicast fast-leave-v2
Syntax: [no] multicast fast-leave-v2
Enabling fast convergence
In addition to sending periodic general queries, an active device sends general queries when it
detects a new port. However, because the device does not recognize the other device's port up
event, multicast traffic might still require up to the query-interval time to resume after a topology
change. Fast convergence allows the device to listen to topology change events in Layer 2 protocols
such as spanning tree, and then send general queries to shorten the convergence time.
If the Layer 2 protocol cannot detect a topology change, fast convergence may not work in some
cases. For example, if the direct connection between two devices switches from one interface to
another, the rapid spanning tree protocol (802.1w) considers this optimization, rather than a
topology change. In this example, other devices will not receive topology change notifications, and
will be unable to send queries to speed up the convergence. Fast convergence works well with the
regular spanning tree protocol in this case.
To enable fast-convergency, enter the following commands.
Brocade(config)#vlan 70
Brocade(config-vlan-70)#multicast fast-convergence
Syntax: multicast fast-convergence
IGMP snooping show commands
This section describes the show commands for IGMP snooping.
Displaying the IGMP snooping configuration
To display the global IGMP snooping configuration, enter the show ip multicast command at any
level of the CLI.
40 FastIron Ethernet Switch IP Multicast Configuration Guide
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